The present disclosure relates to toners suitable for electrophotographic apparatuses.
Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. These toners may be formed by aggregating a colorant with a latex polymer formed by emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex by first forming a seed polymer. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,403,693, 5,418,108, 5,364,729, and 5,346,797, the disclosures of each of which are hereby incorporated by reference in their entirety. Other processes are disclosed in U.S. Pat. Nos. 5,527,658, 5,585,215, 5,650,255, 5,650,256 and 5,501,935, the disclosures of each of which are hereby incorporated by reference in their entirety.
Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins. An issue which may arise with this formulation is that the crystalline polyester may migrate to the surface of the toner particle which, in turn, may adversely affect charging characteristics. Various processes/modifications have been suggested to avoid these issues. For example, the application of shells to the toner particles may be one way to minimize the migration of a crystalline polyester to the toner particle surface. In other cases, charge control agents (CCAs) may be utilized to increase the charge on toner particles. However, most CCAs are only available in solid powder form and need to be converted into aqueous dispersions for emulsion aggregation use. Thus, it can be very difficult, if not impossible, to use many of them efficiently. It thus remains desirable to improve the charging characteristics of EA toners possessing crystalline polyesters.